Many forms of catadioptric lens assemblies have been used to achieve a relatively long focal length in a compact assembly. When a zoom or multi-focal length capability is required, it is known to locate a refractive zoom relay lens group after an intermediate image formed by a catadioptric objective lens group. In such known lens assemblies, the objective lens group and the refractive zoom relay group have been individually corrected to reduce the overall impact of optical abberations on image quality. However, to achieve such individual corrections, it is known to provide the objective lens group with large refractive corrector lenses in front thereof and/or fixed lens groups within the converging beam in advance of the intermediate image. Such lens assemblies are well known, and are shown for example in U.S. Pat. No. 4,235,508 (Kaprelian) and U.S. Pat. No. 4,971,428 (Moskovich).
If such refractive corrector lenses are not provided, the overall resolving power of the lens assembly is reduced and the operating f/number is restricted to values greater than f/10.0 to achieve reasonable optical performance. Such lens assemblies are also well known and are described for example in U.S. Pat. No. 3,529,888 (Buchroeder), see FIG. 4.